1. Field of the Invention
The present invention relates to a power supply device that can be used, for example, in a storage control device and to a power supply method.
2. Description of the Related Art
Storage control devices comprise a storage section that is produced by connecting a multiplicity of hard disk drives in the form of an array. Storage control devices provide a host computer (‘host’ hereinbelow) such as a server with logical storage areas (logical volumes).
In order to increase reliability and high availability and so forth, a storage control device provides the host with redundant storage areas based on RAID (Redundant Array of Independent Disks). Further, storage control devices render various resources such as microprocessors and communication lines redundant. The power supply device of a storage control device is also redundant from the perspective of such high reliability and high availability.
Therefore, in the prior art, a plurality of hard disk drives constitute one group and a plurality of power supply units are allocated to each group (Japanese Patent Application Laid Open No. H11-168832). Normally, when power is supplied from one power supply unit to each of the hard disk drives in a group and the one power supply unit fails, there is an automatic switch to the other power supply unit and power is supplied from the other power supply unit to each of the hard disk drives.
Because each of the groups in the device mentioned in Japanese Patent Application Laid Open No. H11-168832 is provided with a plurality of power supply units, the number of power supply units required increases as the number of groups rises. Further, while the one power supply unit is functioning normally, the other power supply unit does not function. Therefore, because there is a multiplicity of power supply units that are not normally used in the prior art, there is an increase in costs. Further, in the prior art, because there is large number of power supply units, there is the problem that it is difficult to install a greater number of hard disk drives in the storage control device.